From: Peter Zijlstra peterz@infradead.org
commit 584fd3b31889852d0d6f3dd1e3d8e9619b660d2c upstream.
When an ELF object uses extended symbol section indexes (IOW it has a .symtab_shndx section), these must be kept in sync with the regular symbol table (.symtab).
So for every new symbol we emit, make sure to also emit a .symtab_shndx value to keep the arrays of equal size.
Note: since we're writing an UNDEF symbol, most GElf_Sym fields will be 0 and we can repurpose one (st_size) to host the 0 for the xshndx value.
Fixes: 2f2f7e47f052 ("objtool: Add elf_create_undef_symbol()") Reported-by: Nick Desaulniers ndesaulniers@google.com Suggested-by: Fangrui Song maskray@google.com Signed-off-by: Peter Zijlstra (Intel) peterz@infradead.org Tested-by: Nick Desaulniers ndesaulniers@google.com Link: https://lkml.kernel.org/r/YL3q1qFO9QIRL/BA@hirez.programming.kicks-ass.net Signed-off-by: Ben Hutchings ben@decadent.org.uk Signed-off-by: Greg Kroah-Hartman gregkh@linuxfoundation.org --- tools/objtool/elf.c | 25 ++++++++++++++++++++++++- 1 file changed, 24 insertions(+), 1 deletion(-)
--- a/tools/objtool/elf.c +++ b/tools/objtool/elf.c @@ -768,7 +768,7 @@ static int elf_add_string(struct elf *el
struct symbol *elf_create_undef_symbol(struct elf *elf, const char *name) { - struct section *symtab; + struct section *symtab, *symtab_shndx; struct symbol *sym; Elf_Data *data; Elf_Scn *s; @@ -819,6 +819,29 @@ struct symbol *elf_create_undef_symbol(s symtab->len += data->d_size; symtab->changed = true;
+ symtab_shndx = find_section_by_name(elf, ".symtab_shndx"); + if (symtab_shndx) { + s = elf_getscn(elf->elf, symtab_shndx->idx); + if (!s) { + WARN_ELF("elf_getscn"); + return NULL; + } + + data = elf_newdata(s); + if (!data) { + WARN_ELF("elf_newdata"); + return NULL; + } + + data->d_buf = &sym->sym.st_size; /* conveniently 0 */ + data->d_size = sizeof(Elf32_Word); + data->d_align = 4; + data->d_type = ELF_T_WORD; + + symtab_shndx->len += 4; + symtab_shndx->changed = true; + } + sym->sec = find_section_by_index(elf, 0);
elf_add_symbol(elf, sym);